Organic thin film transistor array substrate and liquid crystal display including the same

ABSTRACT

An organic thin film transistor array substrate including a substrate divided into an LCD region and an OTFT region; a first dielectric layer formed on the substrate in the LCD region and having a first uneven portion; an organic semiconducting layer formed on the substrate in the OTFT region; a gate, source, and drain formed in the OTFT region, wherein the source and drain are in contact with the organic semiconducting layer to form a channel between the source and drain; and a pixel electrode formed on the first uneven portion of the first dielectric layer in the LCD region.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an organic thin film transistorarray substrate, and more particularly to an organic thin filmtransistor array substrate in which the dielectric layer underlying thepixel electrode has an uneven structure.

[0003] 2. Description of the Prior Art

[0004] In recent years, organic semiconducting material has drawn manyresearchers' attention and has proven to be one of the most popularcandidates in fabrication of thin film transistors (TFTs) and variouselectronic and optoelectronic devices. Organic semiconducting materialis easy to fabricate, increasing the chance of its future application inflexible displays.

[0005] An organic thin film transistor (OTFT) is a TFT that uses anorganic layer to serve as the active layer and has been used to driveliquid crystal displays (LCDs). In recent years, in order to simplifythe process and decrease production cost, some researchers havedeveloped integration technology that fabricates the LCD and OTFTmonolithically (i.e., on the same substrate).

[0006] For example, Kabushiki Kaisha Toshiba in U.S. Pat. No. 5,355,235discloses an integrated device of LCD and bottom-gate OTFT, in which twoorganic layers are used in the OTFT structure.

[0007] Mitshubishi Denki Kabushiki Kaisha in U.S. Pat. No. 6,060,333discloses a bottom-gate OTFT structure combined with a transmissive orreflective type LCD. For the reflective LCD, the reflector sheet issimply a mirror surface; therefore, the display effect (reflectivity andcontrast) is inferior.

[0008] Hitachi, Ltd. in U.S. Pat. No. 6,300,988 B1 uses a bottom-gateOTFT combined with an LCD. A patterned insulating layer is used to makethe overlying deposited organic semiconducting layer have a pattern,thus separating into a channel region and a non-channel region. Thus,current leakage and crosstalk between devices decreases.

[0009] For the above-mentioned reflective or transflective LCD driven byOTFT, the display effect requires improvement.

SUMMARY OF THE INVENTION

[0010] An object of the present invention is to solve theabove-mentioned problems and provide an organic thin film transistor(OTFT) array substrate and a liquid crystal display (LCD) including theOTFT array substrate, in which the LCD exhibits good display effect.

[0011] To achieve the above object, the OTFT array substrate of thepresent invention includes:

[0012] a substrate divided into a liquid crystal display (LCD) regionand an organic thin film transistor (OTFT) region;

[0013] a first dielectric layer formed on the substrate in the LCDregion and having a first uneven portion;

[0014] an organic semiconducting layer formed on the substrate in theOTFT region;

[0015] a gate, source, and drain formed in the OTFT region, wherein thesource and drain are in contact with the organic semiconducting layer toform a channel between the source and drain; and

[0016] a pixel electrode formed on the first uneven portion of the firstdielectric layer in the LCD region.

[0017] According to the present invention, the process for fabricatingthe organic thin film transistor array substrate includes the followingsteps. A substrate divided into an LCD region and an OTFT region isprovided. A first dielectric layer having a first uneven portion isformed on the substrate in the LCD region. An organic semiconductinglayer is formed on the substrate in the OTFT region. A gate, a source,and a drain are formed in the OTFT region, such that the source and thedrain are in contact with the organic semiconducting layer to form achannel between the source and the drain. A pixel electrode is formed onthe first uneven portion of the first dielectric layer in the LCDregion.

[0018] When the OTFT is a bottom-gate type, the process for fabricatingthe OTFT array substrate includes the following steps. A substratedivided into an LCD region and an OTFT region is provided. A gate isformed on the substrate in the OTFT region, and a dielectric layer isformed in the LCD and OTFT regions to cover the gate. The dielectriclayer is patterned to concurrently form a first dielectric layer havinga first uneven portion in the LCD region and a second dielectric layerin the OTFT region. An organic semiconducting layer is formed on thesecond dielectric layer in the OTFT region. A conductive layer is formedin the LCD and OTFT regions, and the conductive layer is patterned toconcurrently form a pixel electrode on the first uneven portion of thefirst dielectric layer in the LCD region and a source and drain in theOTFT region, such that the source and drain are in contact with theorganic semiconducting layer to form a channel between the source anddrain.

[0019] When the OTFT is a top-gate type, the process for fabricating theOTFT array substrate includes the following steps. A substrate dividedinto an LCD region and an OTFT region is provided. An organicsemiconducting layer is formed on the substrate in the OTFT region. Asource and drain are formed on the organic semiconducting layer in theOTFT region to form a channel between the source and drain. A dielectriclayer is formed on the substrate to cover the source and drain. Thedielectric layer is patterned to form a first dielectric layer having afirst uneven portion in the LCD region and to form a second dielectriclayer on the source and drain in the OTFT region. A metal layer isformed on the first and second dielectric layer, and the metal layer ispatterned to form a pixel electrode on the first dielectric layer in theLCD region and to form a gate on the second dielectric layer in the OTFTregion.

[0020] The present invention also provides a liquid crystal displayincluding an OTFT array substrate. The liquid crystal display includesan OTFT array substrate, a color filter substrate, and liquid crystalinterposed between the OTFT array substrate and the color filtersubstrate. The OTFT array substrate includes:

[0021] a substrate divided into an LCD region and an OTFT region;

[0022] a first dielectric layer formed on the substrate in the LCDregion and having a first uneven portion;

[0023] an organic semiconducting layer formed on the substrate in theOTFT region;

[0024] a gate, source, and drain formed in the OTFT region, wherein thesource and drain are in contact with the organic semiconducting layer toform a channel between the source and drain; and

[0025] a pixel electrode formed on the first uneven portion of the firstdielectric layer in the LCD region.

BRIEF DESCRIPTION OF THE DRAWING

[0026]FIGS. 1a to 1 e are cross-sections illustrating the process flowof the liquid crystal display including the bottom-gate organic thinfilm transistor array substrate according to a first preferredembodiment of the present invention.

[0027]FIG. 2 is a cross-section of the liquid crystal display includingthe bottom-gate organic thin film transistor array substrate accordingto a second preferred embodiment of the present invention.

[0028]FIG. 3 is a cross-section of the liquid crystal display includingthe bottom-gate organic thin film transistor array substrate accordingto a third preferred embodiment of the present invention.

[0029]FIG. 4 is a cross-section of the liquid crystal display includingthe bottom-gate organic thin film transistor array substrate accordingto a fourth preferred embodiment of the present invention.

[0030]FIG. 5 is a cross-section of the liquid crystal display includingthe top-gate organic thin film transistor array substrate according to afifth preferred embodiment of the present invention.

[0031]FIG. 6 is a cross-section of the liquid crystal display includingthe top-gate organic thin film transistor array substrate according to asixth preferred embodiment of the present invention.

[0032]FIG. 7 is a cross-section of the liquid crystal display includingthe top-gate organic thin film transistor array substrate according to aseventh preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0033]FIGS. 1a to 1 e are cross-sections illustrating the process flowof the liquid crystal display including the bottom-gate organic thinfilm transistor array substrate according to a first preferredembodiment of the present invention.

[0034] Referring to FIG. 1a, a substrate 10 divided into a liquidcrystal display (LCD) region and an organic thin film transistor (OTFT)region is provided. A gate 20 is formed on the substrate 10 in the OTFTregion.

[0035] Subsequently, referring to FIG. 1b, a dielectric layer (notshown) is formed in the LCD and OTFT regions to cover the gate 20. Thedielectric layer can be a material that can be patterned. Next, thedielectric layer is patterned to concurrently form a first dielectriclayer 31 in the LCD region and a second dielectric layer 32 in the OTFTregion. The second dielectric layer 32 is lower than the firstdielectric layer 31, thus forming a bank 34. Moreover, the firstdielectric layer 31 in the LCD region has a first uneven portion 31 a,and the second dielectric layer 32 in the OTFT region has a seconduneven portion 32 a with an alignment property. The bank 34 formed inthe OTFT region is used to prevent crosstalk and current leakage.

[0036] According to the present invention, the method of patterning thedielectric layer is not limited. For example, the dielectric layer canbe irradiated by an ion beam through a mask and then developed. Or, ifthe dielectric that can be patterned is a photoresist, the dielectriclayer can be exposed to light through a mask and then be developed. Thedielectric layer can be patterned using one mask in one course. Forexample, by means of a one time light exposure through a gray-tone mask,the first uneven portion 31 a in the LCD region, the bank 34 in the OTFTregion and the second uneven portion 32 a in the bank can beconcurrently formed.

[0037] Alternatively, the dielectric layer can be patterned using twomasks in two courses. For example, the OTFT region is first masked andthe dielectric layer in the LCD region is pattered, thus forming thefirst dielectric layer 31 having the first uneven portion 31 a in theLCD region. Then, the LCD region is masked and the dielectric layer inthe OTFT region is patterned, thus, in the OTFT region, forming the bank34 and the second dielectric layer 32 having the second uneven portion32 a.

[0038] Alternatively, the dielectric layers 31 and 32 can be differentmaterials. For example, two dielectric layers with two differentmaterials are formed in the LCD and OTFT regions respectively. Then,light exposure is performed twice by two masks. Thus, the dielectriclayer 31 having the first uneven portion 31 a in the LCD region and thedielectric layer 32 having the second uneven portion 32 a in the OTFTregion are formed respectively.

[0039] The first and second uneven portions 31 a and 32 a can have thesame alignment direction. Or, the first and second uneven portions 31 aand 32 a can have different alignment directions in order to meetdifferent requirements in the LCD and OTFT regions, and achieve the bestresult.

[0040] In a future step, a pixel electrode 53 will be formed on thefirst uneven portion 31 a of the first dielectric layer 31 in the LCDregion (FIG. 1d). Therefore, in order to make the pixel electrode havebetter reflectivity, the first dielectric layer 31 can be sloped; forexample, it can be a diffusive microslant reflector (DMSR).Alternatively, the first dielectric layer 31 can be fan-shaped toincrease reflectivity. In addition, the second uneven portion 32 a canhave a microgroove form.

[0041] Subsequently, referring to FIG. 1c, an organic semiconductinglayer 41 is formed on the second dielectric layer 32 in the OTFT region.The organic semiconducting layer 41 will align according to thealignment direction of the second uneven portion 32 a. Thus, an alignedorganic semiconducting portion 41 a is formed on the second unevenportion 32 a in a corresponding portion. Since the organicsemiconducting portion 41 a is aligned, carrier mobility increases.

[0042] Subsequently, referring to FIG. 1d, a source 51 and drain 52 areformed in the OTFT region, and a pixel electrode 53 is formed in the LCDregion. The source 51, drain 52, and pixel electrode 53 can be the samematerial and formed in the same course. For example, a conductive layer(not shown) is formed in the LCD and OTFT regions. The conductive layeris preferably a high reflectivity material having a reflectivity higherthan 60%, most preferably in the range of 60% to 95%, for example, ametal material such as aluminum. Next, the conductive layer is patternedto form the source 51, drain 52 and pixel electrode 53. The pixelelectrode 53 is located on the first uneven portion 31 a and willdeposit according to the shape of the first uneven portion 31 a. Thus,the pixel electrode 53 will be aligned, increasing the reflectivity.

[0043] In order for the OTFT to achieve better carrier mobility, thesource 51 and drain 52 are preferably in contact with the organicsemiconducting portion 41 a, such that the channel direction between thesource 51 and drain 52 is the same as the alignment direction of thealigned organic semiconducting portion 41 a. That is, the channeldirection is the same as the alignment direction of the second unevenportion 32 a of the dielectric layer 32.

[0044] Subsequently, still referring to FIG. 1d, a passivation layer 60is formed on the organic semiconducting layer 41 in the OTFT region.Thus far, an organic thin film transistor array substrate 71 isaccomplished. The OTFT array substrate 71 can be used to fabricate areflective liquid crystal display or a transflective liquid crystaldisplay. For a transflective LCD, the aligned pixel electrode 53 in theOTFT array substrate functions as a reflective portion, and thetransmissive portion requires a transparent electrode (not shown) suchas ITO (indium tin oxide).

[0045] Subsequently, referring to FIG. 1e, a color filter substrate 78is provided, and liquid crystal 80 is formed between the OTFT arraysubstrate 71 and the color filter substrate 78 to complete the LCDfabrication.

[0046]FIG. 2 is a cross-section of the liquid crystal display includinga bottom-gate OTFT array substrate according to a second preferredembodiment of the present invention. The liquid crystal display includesan OTFT array substrate 72, a color filter substrate 78, and liquidcrystal 80 interposed between the OTFT array substrate 72 and the colorfilter substrate 78.

[0047] The OTFT array substrate 72 of FIG. 2 includes a substrate 10divided into an LCD region and an OTFT region; a gate 20 formed on thesubstrate 10 in the OTFT region; a first dielectric layer 31 formed onthe substrate 10 in the LCD region and having a first uneven portion 31a; a second dielectric layer 322 formed on the gate 20 in the OTFTregion; an organic semiconducting layer 42 formed on the seconddielectric layer 322 in the OTFT region; a source 51 and drain 52 bothformed on the organic semiconducting layer 42; a pixel electrode 53formed on the first uneven portion 31 a of the first dielectric layer 31in the LCD region; and a passivation layer 60 formed on the organicsemiconducting layer 42.

[0048] The LCDs of FIG. 2 and FIG. 1e have similar structures. Thedifference resides in that the second dielectric layer 322 in FIG. 2does not have the second uneven portion. Therefore, the organicsemiconducting layer 42 overlying the second dielectric layer has nomolecular alignment.

[0049] The process for fabricating the LCD of FIG. 2 is almost the sameas FIG. 1e; therefore, detailed cross-sections illustrating the processflow are omitted. First, a substrate 10 divided into an LCD region andan OTFT region is provided. A gate 20 is formed on the substrate 10 inthe OTFT region. Next, a dielectric layer (not shown) is formed in theLCD and OTFT regions to cover the gate 20. Next, the dielectric layer ispatterned to concurrently form a first dielectric layer 31 having afirst uneven portion 31 a in the LCD region and a second dielectriclayer 322 in the OTFT region. Next, an organic semiconducting layer 42is formed on the second dielectric layer 322 in the OTFT region. Next, aconductive layer (not shown) is formed in the LCD and OTFT regions andis then patterned to concurrently form a pixel electrode 53 on the firstuneven portion 31 a of the first dielectric layer 31 in the LCD region,and a source and drain in the OTFT region. Next, a passivation layer isformed on the organic semiconducting layer 42 to complete the OTFT arraysubstrate 72. Finally, liquid crystal 80 is formed between the OTFTarray substrate 72 and a color filter substrate 78.

[0050]FIG. 3 is a cross-section of the liquid crystal display includinga bottom-gate OTFT array substrate according to a third preferredembodiment of the present invention. The structure and process of FIG. 3are similar to FIG. 2; therefore, detailed cross-sections illustratingthe process flow are omitted. FIG. 3 differs from FIG. 2 in that afterpatterning the dielectric layer and before forming the organicsemiconducting layer 43, an alignment film 93 is formed on the seconddielectric layer 322 in the OTFT region. Then, the organicsemiconducting layer 43 is formed on the alignment film 93. Thus, theorganic semiconducting layer 43 will align according to the alignmentdirection of the alignment film 93.

[0051] Formation of the alignment film is not limited. For example, afilm such as a PI (polyimide) film is first formed and then rubbing isperformed to form the alignment film 93 with alignment over the entiresurface, as shown in FIG. 3. Or, alternatively, the alignment film canbe made to have different alignment directions in different regions. Forexample, refer to FIG. 4, showing a cross-section of the liquid crystaldisplay including a bottom-gate OTFT array substrate according to afourth preferred embodiment of the present invention. Symbol 94 refersto an alignment film, symbol 44 an organic semiconducing layer, symbol74 an OTFT array substrate, and other symbols the same as FIG. 3 referto the same elements. As can be seen from FIG. 4, only the portion ofthe film 94 labeled as 94 a is aligned. Thus, the organic semiconductinglayer 44 can be controlled to have partial alignment. As shown in FIG.4, only the portion labeled as 44 a is aligned.

[0052] The process for forming the alignment film 94 with partialalignment in FIG. 4 is described below. A third dielectric layer (notshown) is formed and then irradiated by an ion beam through a mask.Next, developing is performed to obtain the alignment film 94 withpartial alignment. Alternatively, a photoresist layer (not shown) isformed and then exposed to light through a mask, and developing is thenperformed to obtain the alignment film 94 with partial alignment.Alternatively, a photoalignment organic layer (not shown) is formed andthen irradiated by a polarized light through a mask. Thus, the organiclayer becomes the alignment film 94 with partial alignment.

[0053]FIG. 5 is a cross-section of the liquid crystal display includinga top-gate OTFT array substrate according to a fifth preferredembodiment of the present invention. The liquid crystal display includesan OTFT array substrate 75, a color filter substrate 78, and liquidcrystal 80 formed between the OTFT array substrate 75 and the colorfilter substrate 78.

[0054] The OTFT array substrate 75 of FIG. 5 includes a substrate 10divided into an LCD region and an OTFT region; an organic semiconductinglayer 45 formed on the substrate 10; a source 51 and drain 52 formed onthe organic semiconducting layer 45 in the OTFT region; a firstdielectric layer 37, having a first uneven portion 37 a, formed in theLCD region; a second dielectric layer 38 formed on the source 51 anddrain 52 in the OTFT region; a pixel electrode 57 formed on the firstuneven portion 37 a of the first dielectric layer 37 in the LCD region;and a gate 58 formed on the second dielectric layer 38 in the OTFTregion.

[0055] Fabrication of the LCD of FIG. 5 is almost the same as mentionedabove and is described in the following. First, a substrate 10 dividedinto an LCD region and an OTFT region is provided. An organicsemiconducting layer 45 is formed on the substrate 10 in the OTFTregion. Next, a source 51 and drain 52 are formed on the organicsemiconducting layer 45 in the OTFT region and a channel is formedbetween the source and drain. A dielectric layer (not shown) is formedon the substrate 10 to cover the source 51 and drain 52. Next, thedielectric layer is patterned to form a first dielectric layer 37 havinga first uneven portion 37 a in the LCD region, and a second dielectriclayer 38 on the source 51 and drain 52 in the OTFT region. Next, a metallayer (not shown) is formed on the first and second dielectric layers 37and 38. The metal layer is patterned to form a pixel electrode 57 on thefirst dielectric layer 37 in the LCD region, and a gate 58 on the seconddielectric layer 38 in the OTFT region. Thus far, an OTFT arraysubstrate 75 is accomplished. Finally, liquid crystal 80 is formedbetween the OTFT array substrate 75 and a color filter substrate 78 tocomplete the LCD.

[0056]FIG. 6 is a cross-section of the liquid crystal display includinga top-gate OTFT array substrate according to a sixth preferredembodiment of the present invention. The structure and process of FIG. 6are similar to FIG. 5; therefore, detailed description is omitted. InFIG. 6, symbol 96 refers to an alignment film, symbol 46 an organicsemiconducting layer, symbol 76 an OTFT array substrate, and othersymbols the same as FIG. 5 refer to the same elements. FIG. 6 differsfrom FIG. 5 mainly in that the alignment film 96 is formed on thesubstrate 10 in the OTFT region before formation of the organicsemiconducting layer 46. Thus, the organic semiconducting layer 46 willalign according to the alignment direction of the alignment film 96.Formation of the alignment film 96 is similar to the above descriptionand is omitted here. The alignment film 96 is aligned over the entiresurface.

[0057]FIG. 7 is a cross-section of the liquid crystal display includinga top-gate OTFT array substrate according to a seventh preferredembodiment of the present invention. The structure and process of FIG. 7are similar to FIG. 6; therefore, detailed description is omitted. InFIG. 7, symbol 97 refers to an alignment film, symbol 47 an organicsemiconducting layer, symbol 77 an OTFT array substrate, and othersymbols the same as FIG. 5 refer to the same elements. FIG. 7 differsfrom FIG. 6 mainly in that only the portion of the alignment film 97labeled as 97 a is aligned. Thus, the organic semiconducting layer 47can be controlled to have partial alignment. That is, only the portionlabeled as 47 a has alignment. The process for forming the alignmentfilm with partial alignment is the same as described above and detaileddescription is omitted.

[0058] In conclusion, the present invention forms the first dielectriclayer having the first uneven portion in the LCD region; thus, theoverlying pixel electrode has better reflectivity and display effect.Moreover, when the first dielectric layer in the LCD region is formed,the second dielectric layer having the second uneven portion withalignment can be formed in the OTFT region. Thus, the overlyingsemiconducting layer can align according to the alignment direction ofthe second uneven portion, thus increasing the carrier mobilityefficiency and improving electric properties.

[0059] The foregoing description of the preferred embodiments of thisinvention has been presented for purposes of illustration anddescription. Obvious modifications or variations are possible in lightof the above teaching. The embodiments chosen and described provide anexcellent illustration of the principles of this invention and itspractical application to thereby enable those skilled in the art toutilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated. All suchmodifications and variations are within the scope of the presentinvention as determined by the appended claims when interpreted inaccordance with the breadth to which they are fairly, legally, andequitably entitled.

What is claimed is:
 1. An organic thin film transistor array substratecomprising: a substrate divided into a liquid crystal display (LCD)region and an organic thin film transistor (OTFT) region; a firstdielectric layer formed on the substrate in the LCD region and having afirst uneven portion; an organic semiconducting layer formed on thesubstrate in the OTFT region; a gate, source, and drain formed in theOTFT region, wherein the source and drain are in contact with theorganic semiconducting layer to form a channel between the source anddrain; and a pixel electrode formed on the first uneven portion of thefirst dielectric layer in the LCD region.
 2. The organic thin filmtransistor array substrate as claimed in claim 1, further comprising asecond dielectric layer underlying the organic semiconducting layer inthe OTFT region, wherein the second dielectric layer has a second unevenportion, and the second uneven portion has an alignment property, suchthat the organic semiconducting layer aligns according to the alignmentof the second uneven portion.
 3. The organic thin film transistor arraysubstrate as claimed in claim 2, wherein the first and second dielectriclayer are composed of the same material and are formed in the samecourse.
 4. The organic thin film transistor array substrate as claimedin claim 1, wherein the pixel electrode and any one, or a combination ofthe gates, source or drain are composed of the same material and formedin the same course.
 5. The organic thin film transistor array substrateas claimed in claim 1, wherein the pixel electrode is highly reflectivematerial having a reflectivity higher than 60%.
 6. The organic thin filmtransistor array substrate as claimed in claim 5, wherein the pixelelectrode is metal.
 7. The organic thin film transistor array substrateas claimed in claim 1, wherein the second dielectric layer in the OTFTregion is located lower than the first dielectric layer in the LCDregion to form a bank.
 8. The organic thin film transistor arraysubstrate as claimed in claim 2, wherein the channel between the sourceand drain has a channel direction the same as the alignment direction ofthe second uneven portion of the second dielectric layer.
 9. The organicthin film transistor array substrate as claimed in claim 1, wherein theorganic thin film transistor is bottom-gate type and the organic thinfilm transistor array substrate comprises: a substrate divided into anLCD region and an OTFT region; a gate formed on the substrate in theOTFT region; a first dielectric layer formed on the substrate in the LCDregion and having a first uneven portion; a second dielectric layerformed on the gate in the OTFT region and having a second unevenportion, the second uneven portion having an alignment property; anorganic semiconducting layer formed on the second uneven portion of thesecond dielectric layer in the OTFT region, such that the organicsemiconducting layer aligns according to the alignment of the seconduneven portion; a source and drain both formed in the OTFT region,wherein the source and drain are in contact with the organicsemiconducting layer to form a channel between the source and drain; anda pixel electrode formed on the first uneven portion of the firstdielectric layer in the LCD region.
 10. The organic thin film transistorarray substrate as claimed in claim 1, wherein the organic thin filmtransistor is bottom-gate type and the organic thin film transistorarray substrate comprises: a substrate divided into an LCD region and anOTFT region; a gate formed on the substrate in the OTFT region; a firstdielectric layer formed on the substrate in the LCD region and having afirst uneven portion; a second dielectric layer formed on the gate inthe OTFT region; an organic semiconducting layer formed on the seconddielectric layer in the OTFT region; a source and drain both formed inthe OTFT region, wherein the source and drain are in contact with theorganic semiconducting layer to form a channel between the source anddrain; and a pixel electrode formed on the first uneven portion of thefirst dielectric layer in the LCD region.
 11. The organic thin filmtransistor array substrate as claimed in claim 10, further comprising analignment film between the second dielectric layer and the organicsemiconducting layer, such that the organic semiconducting layer alignsaccording to the alignment of the alignment film.
 12. The organic thinfilm transistor array substrate as claimed in claim 11, wherein thealignment film has an alignment portion, such that the organicsemiconducting layer aligns according to the alignment of the alignmentportion of the alignment film.
 13. The organic thin film transistorarray substrate as claimed in claim 1, wherein the organic thin filmtransistor is top-gate type and the organic thin film transistor arraysubstrate comprises: a substrate divided into an LCD region and an OTFTregion; an organic semiconducting layer formed on the substrate in theOTFT region; a source and a drain both formed on the semiconductinglayer in the OTFT region; a first dielectric layer formed in the LCDregion and having a first uneven portion; a second dielectric layerformed on the source and drain in the OTFT region; a pixel electrodeformed on the first uneven portion of the first dielectric layer in theLCD region; and a gate formed on the second dielectric layer in the OTFTregion.
 14. The organic thin film transistor array substrate as claimedin claim 13, further comprising an alignment film between the substrateand the organic semiconducting layer in the OTFT region, such that theorganic semiconducting layer aligns according to the alignment of thealignment film.
 15. The organic thin film transistor array substrate asclaimed in claim 14, wherein the alignment film has an alignmentportion, such that the organic semiconducting layer aligns according tothe alignment of the alignment portion of the alignment film.
 16. Aprocess for fabricating an organic thin film transistor array substrate,comprising the following steps: providing a substrate divided into anLCD region and an OTFT region; forming a first dielectric layer having afirst uneven portion on the substrate in the LCD region; forming anorganic semiconducting layer on the substrate in the OTFT region;forming a gate, a source, and a drain in the OTFT region, such that thesource and the drain are in contact with the organic semiconductinglayer to form a channel between the source and the drain; and forming apixel electrode on the first uneven portion of the first dielectriclayer in the LCD region.
 17. The process as claimed in claim 16, whereinthe organic thin film transistor is bottom-gate type and the processcomprises the following steps: providing a substrate divided into an LCDregion and an OTFT region; forming a gate on the substrate in the OTFTregion; forming a dielectric layer in the LCD and OTFT regions to coverthe gate; patterning the dielectric layer to concurrently form a firstdielectric layer having a first uneven portion in the LCD region and asecond dielectric layer in the OTFT region; forming an organicsemiconducting layer on the second dielectric layer in the OTFT region;and forming a conductive layer in the LCD and OTFT regions, patterningthe conductive layer to concurrently form a pixel electrode on the firstuneven portion of the first dielectric layer in the LCD region and asource and drain in the OTFT region, such that the source and drain arein contact with the organic semiconducting layer to form a channelbetween the source and drain.
 18. The process as claimed in claim 17,wherein the step of patterning the dielectric layer further comprises:forming the second dielectric layer having a second uneven portion inthe OTFT region, wherein the second uneven portion has alignmentproperty, such that the organic semiconducting layer aligns according tothe alignment of the second uneven portion.
 19. The process as claimedin claim 18, wherein the step of patterning the dielectric layer furthercomprises: forming the second dielectric layer lower than the firstdielectric layer to form a bank.
 20. The process as claimed in claim 18,wherein the step of forming the source and drain further comprises:making the channel between the source and drain to have a channeldirection the same as the alignment direction of the second unevenportion of the second dielectric layer.
 21. The process as claimed inclaim 18, wherein the step of forming the first and second unevenportions comprises: irradiating the dielectric layer by an ion beamthrough a mask and then developing.
 22. The process as claimed in claim18, wherein the dielectric layer is a photoresist layer and the step offorming the first and second uneven portions comprises: exposing thedielectric layer by light through a mask and then developing.
 23. Theprocess as claimed in claim 17, further comprising, after patterning thedielectric layer and before forming the organic semiconducting layer,forming an alignment film on the second dielectric layer in the OTFTregion, such that the organic semiconducting layer aligns according tothe alignment of the alignment film.
 24. The process as claimed in claim23, wherein the step of forming the alignment film comprises: forming athird dielectric layer, irradiating the third dielectric layer by an ionbeam through a mask, and then developing.
 25. The process as claimed inclaim 23, wherein the step of forming the alignment film comprises:forming a photoresist layer, exposing the photoresist layer by lightthrough a mask, and then developing.
 26. The process as claimed in claim23, wherein the step of forming the alignment film comprises: forming aphotoalignment organic layer; and irradiating the photoalignment organiclayer by polarized light through a mask, such that the photoalignmentorganic layer becomes an alignment film having molecular alignment. 27.The process as claimed in claim 18, wherein the step of forming thefirst and second uneven portions comprises: masking the OTFT region andforming a first dielectric layer having a first uneven portion in theLCD region; and masking the LCD region and forming a second dielectriclayer having a second uneven portion in the OTFT region.
 28. The processas claimed in claim 16, wherein the organic thin film transistor istop-gate type and the process comprises: providing a substrate dividedinto an LCD region and an OTFT region; forming an organic semiconductinglayer on the substrate in the OTFT region; forming a source and drain onthe organic semiconducting layer in the OTFT region to form a channelbetween the source and drain; forming a dielectric layer on thesubstrate to cover the source and drain; patterning the dielectric layerto form a first dielectric layer having a first uneven portion in theLCD region and to form a second dielectric layer on the source and drainin the OTFT region; forming a metal layer on the first and seconddielectric layer; and patterning the metal layer to form a pixelelectrode on the first dielectric layer in the LCD region and to form agate on the second dielectric layer in the OTFT region.
 29. The processas claimed in claim 28, wherein the step of patterning the dielectriclayer comprises: irradiating the dielectric layer by an ion beam througha mask and then developing.
 30. The process as claimed in claim 28,wherein the dielectric layer is a photoresist layer and the step -ofpatterning the dielectric layer comprises: exposing the dielectric layerby light through a mask and then developing.
 31. The process as claimedin claim 28, further comprising, before forming the organicsemiconducting layer, the following step: forming an alignment film onthe substrate in the OTFT region, such that the organic semiconductinglayer aligns according to the alignment of the alignment film.
 32. Theprocess as claimed in claim 31, wherein the step of forming thealignment film comprises: forming a third dielectric layer, irradiatingthe third dielectric layer by an ion beam through a mask, and thendeveloping.
 33. The process as claimed in claim 31, wherein the step offorming the alignment film comprises: forming a photoresist layer,exposing the photoresist layer by light through a mask, and thendeveloping.
 34. The process as claimed in claim 31, wherein the step offorming the alignment film comprises: forming a photoalignment organiclayer; and irradiating the photoalignment organic layer by polarizedlight through a mask, such that the photoalignment organic layer becomesan alignment film having molecular alignment.
 35. A liquid crystaldisplay including an organic thin film transistor array substrate,comprising an organic thin film transistor array substrate, a colorfilter substrate, and liquid crystal interposed between the organic thinfilm transistor array substrate and the color filter substrate, whereinthe organic thin film transistor array substrate comprises: a substratedivided into an LCD region and an OTFT region; a first dielectric layerformed on the substrate in the LCD region and having a first unevenportion; an organic semiconducting layer formed on the substrate in theOTFT region; a gate, source, and drain formed in the OTFT region,wherein the source and drain are in contact with the organicsemiconducting layer to form a channel between the source and drain; anda pixel electrode formed on the first uneven portion of the firstdielectric layer in the LCD region.
 36. The liquid crystal display asclaimed in claim 35, wherein the organic thin film transistor arraysubstrate further comprises a second dielectric layer underlying theorganic semiconducting layer in the OTFT region, wherein the seconddielectric layer has a second uneven portion with alignment property,such that the organic semiconducting layer aligns according to thealignment of the second uneven portion.
 37. The liquid crystal displayas claimed in claim 36, wherein the first and second dielectric layerare made of the same material and are formed in the same course.
 38. Theliquid crystal display as claimed in claim 35, wherein the pixelelectrode and any one, or a combination of the gate, source or drain aremade of the same material and formed in the same course.
 39. The liquidcrystal display as claimed in claim 35, wherein the pixel electrode ishighly reflective material having a reflectivity of higher than 60%. 40.The liquid crystal display as claimed in claim 39, wherein the pixelelectrode is metal.
 41. The liquid crystal display as claimed in claim36, wherein the second dielectric layer in the OTFT region is locatedlower than the first dielectric layer in the LCD region to form a bank.42. The liquid crystal display as claimed in claim 36, wherein thechannel between the source and drain has a channel direction the same asthe alignment direction of the second uneven portion of the seconddielectric layer.